Saturday, August 1, 2020

Cleaning another watch

Another watch needed cleaning... this one is a Waltham pocket watch.  Again, I am heedless of the advice to avoid antiques.  This watch appears to have been completed in 1891, roughly 129 years ago.

This post shows my usual process for cleaning.  I'm not a professional, so I probably do things in a weird way, so don't copy my steps if you don't know what you're doing...  Of course, I am not really sure I know what I'm doing, but here is someone who does...

After popping off the bezel (holding a glass face), the first step is to remove the hands.


Removing the two case screws lets the movement drop through the front of the case.  Immediately secure it in the movement holder so that you don't damage it.


The dial is held in by three small screws on the side, which can be withdrawn just a little bit to release the dial.  Removing the screws all the way is unnecessary and increases the risk you'll lose them.  (They are also a bit of a pain to reinstall if they fall out!)


Once the dial is off, be very careful not to crush the seconds hand arbor.  I did that once on a wristwatch.  Fortunately, I was able to obtain a replacement part. Always pay attention to where the seconds hand arbor is!  I often have to be changing the grip of the movement holder to access different parts, so I have to remind myself to check for the seconds hand arbor every single time before I choose a new placement.

I like to remove the motion work so that I don't lose anything once the movement is flipped over.  Most motion works aren't held in by anything but the dial, and since the dial is now removed, they're not held in at all!

Like many old American-made watches, the winding works are rather weird.


Here are some parts of the winding work that are notable.  This part is particularly crazy. It retracts (counterclockwise movement) during winding, and then springs back to the way the photo shows when the winding ceases.  Check out the long-neck spring on the left!
 

The crown wheel for the winding stem is a two piece assembly with a pin that runs through the center.  The retaining spring is really interesting-looking, and holds the pin head in place.


Every American watch I've opened has a different winding mechanism.  I have a funny feeling that the diversity of winding works on American watches has to do with patent laws, but I am not really sure.  Swiss watches all basically use the same (Breguet) winding works.  Although the Swiss works have their problems, I am pretty comfortable with their fail mechanisms.  American movements are harder to figure out!  Fortunately, this watch's winding works were in perfect working order, so I didn't have to investigate them too closely.  However, it took me a while to find the click (buried under the barrel, oddly) so that I could take the power down before proceeding.

Once the power is removed, the next step is to carefully remove the balance.


I recently learned from Nicholas Hacko's really awesome website that a good way to manage the balance is to hold the complete balance by the cock, letting the balance dangle.  That makes sense (since this is how you vibrate the hairspring if you need to change anything about it), and is super easy to get the balance engaged properly with the fork.  However, it is also a bit unnerving to have the balance "sproinging about" as you remove/install it.

Here is the balance (placed safely upside down).
 

In order to clean the balance cock jewel, there is a small grub screw holding the hairspring attachment point.


A zoom in on the jewel shows it to be in good condition.


There is a small chip in the jewel (just to the right of the hole in the picture below), but I think it's out of the way enough that it won't damage the balance pivot.


That's good, so I just put the balance cock (wholesale) into the ultrasonic cleaner.  By rights, I should remove the cap jewel, but since I didn't see any grime in it, I didn't want to go through that hassle.  The other balance jewel is in similarly good condition.


Here's the other side of the lower balance jewel.


My next step is to remove the lever fork, which goes into the ultrasonic on its own so that none of the "bigger" parts move around to squash it.  The fork cock has no jewel, but is not too worn either, even thought its hole is slightly oblong.  Not bad for being 129 years old!


Here's the movement after the fork and its cock are removed for cleaning.


This watch has a single plate for the train, so that comes off next and goes in the ultrasonic cleaner.


I usually have to clean the plate holes, too.  The official material is "peg wood", which (being a carpenter) seems a bit mysterious to me.  What is a "peg tree" anyway?  Toothpicks work just fine if you're gentle.


Here are the train wheels, removed and ready to be cleaned.


After getting the train wheels in the cleaner, I took out the winding barrel.  There was a surprise waiting there!  Something is very weird about that click spring...  (The click arbor is in the right of the image.  I have already removed the click.)


Let's change the lighting for a better look...


What?!  The spring evidently broke at some point in the past.  Rather than fixing it "properly", the watchmaker soldered a piece of wire onto the end in a rather awkward way, leaving both ends raw.  I thought about replacing this altogether, but decided to leave that for later.  It does work, so I guess it can stay.. 

Once I got over that fright, I disassembled the barrel and cleaned it completely.  Usually, I leave the of a watch barrel alone, but this one was particularly grimy.  The click is the part all the way on the right below.


Here's the main spring removed from the barrel.  Based on its curvature it is definitely not new, but it ought to still have enough power to run the watch.


I just wiped the spring clean and then regreased it with mechanic's Slip-It.  That seems to be a mild but effective grease.  It's also not very messy, which is a major plus. 

I had a little trouble keeping the spring end hook attached to the barrel.  Unlike most movements that have the spring hook in-plane, and the hook engages with the inner wall of the barrel, this one had a pin that fits a hole in the lid of the barrel.  The pin kept popping out of its hole.  After a bit of wrestling, I got it back in place.

At this point, the watch is completely apart.  It's merely a matter of waiting for everything to take time in the cleaner.  I had to use isopropyl alcohol to loosen some of the grime, clean off fingerprints, and carefully scrub some parts.  But all in all, this watch was much cleaner than some clocks I've fixed! 

The process from there on out is the slow, careful reassembly, basically the reverse of everything just shown.  Reassembly is also the time when things have a habit of breaking, but fortunately that did not happen!  Everything just fit together as it ought, aside from a few minor missteps that were quickly resolved.

The only new step is the oiling...  I use a very fine oiler, which looks like a small spoon under the microscope, but basically is a very fine needle.


It pays to be sparing with the oil or else it will run out of the oil sinks.  I usually add a bit less than a full "drop" of oil; just enough to about 1/3 fill a sink.

Once back together, the watch started right up with just shy of a quarter of a turn on the winding stem.  Great news!

Sunday, July 5, 2020

Small shepherd's sundial

Some time ago, I made a simple wooden shepherd's sundial.  It's crude and doesn't work well, but I set it on a lanyard and occasionally use it.  When I decided to use it recently, my wife asked for a small one as a necklace.  Commissioned artwork time!

Since I wanted the sundial to be stylish as well as functional, I thought a bit about materials.  I ended up with a simple design that uses 3/8" copper tubing.  It's the same stuff that you can get at the hardware store for various plumbing jobs, but it's small enough for the task.  I traced out the hour lines using a short python script, and printed them out for use as a guide.


The gnomon is held in a steel cylinder with a slight lip to retain it inside the copper tubing, which has a matching (reverse) lip bored in the end.  You slide the cylinder in from the bottom of the sundial.  Boring the copper was a bit of a problem until I got the boring bit set properly.  I also ended up bursting through the side of the first cylinder because I didn't correctly account for the thickness of the tubing. 

I cut the tubing with a jeweler's saw and filed it to final shape for the noon curve.   The cylinder has two drillings: an axial drilling for the hanging loop and a radial drilling for the gnomon.  The hanging loop is just a piece of brass wire bent into a loop at the top.  I thought of soldering it in place, but decided not to.  I hammered the bottom end of the wire into a small rivet, so the loop is free to turn. 

Here is a trial assembly.


I spent considerable time polishing the copper, the pin, and the cylinder.  The machining was not too arduous, though it did take a few tries, but the engraving was much more tricky.

Here's the final product.


I did not use a watchmaker's square graver (too unwieldy on the round surface) nor the more usual round graver (difficult to get it to bite consistently) to do the engraving.  After a bit of trial on a scrap piece of copper tubing, I found that a very small screwdriver that I had previously sharpened to a narrow cutting blade worked much better for engraving.

To keep everything aligned, I taped the printout to the surface of the copper, and cut through the paper.  This got the copper marked in roughly the right places.  Then I removed the paper and finished the engraving under the microscope.  This took about an hour, and was a bit nerve-wracking because every slip-up is visible.  I'm not too proud of how the engraving came out -- many slips, wiggles, and other awful mishaps are visible if you look closely.  However, it doesn't look embarrassingly bad if you don't use a microscope. 

The sundial certainly looks nice enough on its own, but I am not sure how practical the shiny surface will be in use.  It's cloudy now, which might be for the best!

Saturday, June 27, 2020

Fixing a violin bow ferrule

The ferrule on my son's violin bow snapped open.  This is the little metal piece near the end of the frog...  You can see the split along the edge.  I'm holding the two pieces together in this picture.


This not being a particularly expensive bow, I decided to try my hand at repairing it.  I am not a luthier -- any more than I am a watchmaker or clockmaker; that doesn't stop me -- and this is not a usual repair...  That said, it's not particularly difficult either.  I was inspired by the instructions on this page.

These are the parts that need to be removed to access the ferrule.
 


The idea is that ferrules are typically soldered together from two pieces: a flat piece and a round piece.  This video explains the process, which reminds me of many jewelry soldering tasks.

But since this bow was not that expensive, I think the ferrule was assembled as one piece.  From looking inside the break, it looked like the ferrule was brass plated with something shiny.  It is slightly magnetic, so perhaps it's stainless steel? 

In any case, I can solder brass with a little flux!  So apply flux wherever you want solder... and don't put it where you don't!


The task is basically a soldering job and a jewelry job.  For that, I like to use fairly soft, lead-free silver solder.  It's easy enough to slice off a small chip to use with a chisel.


Bind the works up with soft iron wire.  This holds the ferrule together as you solder, and gives you a handle that is far from the flame!


If you're careful, you can plant the solder chip in the blob of flux.  Then, when you heat the joint, the flux melts, and then the solder follows the flux into the joint.  Be very careful to apply heat slowly, so that the flux doesn't splatter and knock the solder away!  Also, if you overheat the joint, the flux will burn away, leaving oxidization everywhere, and then the solder won't stick to the joint.  Worse, it will probably stick somewhere else...

I didn't photograph the soldering process itself because I didn't have enough hands free.  Once the soldering is done, there is some scaling, oxidization, and flux.


I like to dissolve most of the flux in isopropyl alcohol.


Then you can file away the excess scaling and solder (gently!)...


Try the fit of the ferrule on the frog. 


File until it slides on with some friction, but not too much.  It's difficult to describe what you're after, but it's very easy to feel what "too tight" feels like.  I also interleave the job of polishing with the job of fitting, since polishing the inside of the ferrule adjusts the fit to the frog.  Because the solder made a bit of a fillet, which I wanted to retain, I also filed the frog a little bit.  You wouldn't want to do this to an expensive bow, but this bow had a plastic frog, and didn't seem to mind the offense.

To start the polishing, I start with sandpaper.  Things were clean enough that I could start to sand with 600 grit


... and then move to 1500 grit


... and finally polish all surfaces.


I like to use premade polishing paste in a stick.  Even though it's intended to be used on a powered buffing wheel, I just scrape the stick onto a piece of fabric and polish by hand.  You have better control of the polishing of small parts that way.


Keep trying the fit of the ferrule on the frog as you polish, until it fits perfectly and is polished.

Slide the ferrule onto the bow hair.  Make sure it's oriented in the right direction!


This bow has the hair anchored by a screw...  Slide the cover on...


Slide the ferrule on..


And press the spreader in place.  The spreader may be a bit tighter than before, since the solder joint takes up some space.  Don't force it!  I did force, and was rewarded with a split solder joint.  I had to start back at the beginning!  If it doesn't fit, carefully file the spreader so that it does....


And finish the job by reassembling the frog.


Monday, June 8, 2020

Antiques and heirlooms

Among amateur watch repairers, it is good advice refuse to work on antiques or valuable heirlooms.  Doing so without sufficient experience can lead to frustration!  Old watches also have non-standard parts and other oddities that can trip up the unsuspecting would-be repairer.  I have followed this advice until recently... and ended up in a bit of an adventure.

What tempted me down this path was an antique heirloom watch that was in very poor shape.



It was apparently my great grandmother's watch.  It is quite pretty, but when I received it, it had not been well kept by its owner.  Furthermore, it had been to some very poor watchmakers!  Slowly, over the course of three years, I made a number of repairs, none too difficult:
  1. I replaced the missing glass with an acrylic face.
  2. The case wouldn't close because it was slightly out of round... I put it back into the round, so the case opens and closes correctly.
  3. I remade a case screw that someone had snapped the head in half (!). There are marks on the plate where the screwdriver skidded off after snapping the screw, so clearly way too much force was involved.  Ouch!
  4. The winding stem that was acting up, because a brake was tensioned incorrectly.
  5. I put the hairspring back in order because it was twisted badly.
  6. Finally, recently, I took the movement apart and cleaned it.  This was completely uneventful.
It now runs reliably, but gains about 5 minutes per day.  That's terrible, of course.  But given that I don't have a replacement hairspring and given the age of the watch, it's well within what I'm willing to tolerate.

I had a very different experience -- and it's not over -- with a watch from my wife's family.



This watch wouldn't run, but didn't have anything visibly wrong with it.  Upon disassembly, I found that the lever fork cock was ever so slightly bent and was pinning the fork down.  Since it couldn't move very well, that kept the train stuck.  That wasn't the only problem...

As I was reassembling the balance, I was a bit less careful than I should have been.  I noticed the balance was not able to turn freely in both directions.  The balance was simply on the wrong side of the fork, and needed to be carefully lifted over the fork.  Unfortunately,  I couldn't visualize what was wrong.  Instead of the correct move, I gave the balance a sound push the other way.  That was not a good plan, and I really did know better!  Disaster!  The impulse pallet jewel was shattered!

After carefully sizing the missing pallet (seems to be about 19/1000"), I realized that it would be useful to make the pallet out of blued steel.  It should have nearly the same characteristics, and it should "just work."  (I also ordered a ruby impulse pallet, but I'm not confident of my measurements...)

It took five tries to make and install the impulse pallet, because I lost the first three pallets I made, and although the fourth worked, it was very poorly made.  The fifth looks nice enough and seems to be working. 

Of course, the first step was to disassemble the balance.  I removed the old pallet by heating the roller table with a soldering iron with a fine tip at roughly 250 degrees F.  Using a needle, I cracked off all the old shellac.

First, I trued up the end of a 0.5mm blued steel rod, using an arkansas slip.


After truing, I rounded and burnished the end.  Next, under the microscope, and on a soft piece of wood, I ground a flat surface using the arkansas slip.  In the picture below, the flat is visible as the slight smear at the end of the rod.  (The flat is about 1 mm long.)


This made the rod into a D shape.  I kept grinding the flat until the rod barely entered the hole in the roller table.  Then, I burnished the flat surface.

Unfortunately, the rod was too large to fit the slot in the lever fork.


So, I ground a fine taper to the rod by hand, by eye, under the microscope until the rod would just barely bind in the lever fork as I rotated it with the tip in the fork.

Then I switched to a steel burnisher to smooth the surface of the rod.  After burnishing, the rod freely fit the lever fork, with the base of the taper still fitting the roller table.

To cut the pallet off the rod, it's important to cut it to the precise length.  Since I ended up making five pallets, I was able to zero in on the correct length by comparing with an earlier attempt.  But in any case, I reversed the rod in the pin vise, and then used a narrow file as a saw to slice off the pallet.


Once again, I switched back to the arkansas slip to true the end, and then polished it with the burnisher.  Even though this cut end is completely invisible, this was an important step because the cutting raised burrs.  Burnishing removed those burrs.

OK, now the pallet was small!  It's the apparent "grain of sand" on the left of the frame in the balance cock in the picture below.


Getting the impulse pallet into the hole in the roller table was... irritating.  The pallet is slippery by design, and rounded... which means that holding it too tightly (or gripping the wrong surface) with tweezers will launch it across the room.  I lost three attempts irretrievably and lost another one for a very long time.  Eventually I got it pressed in place.

To anchor the pallet, I gripped the balance in surgical clamps and applied shellac.


Someone before me was way too liberal with the shellac and glued together several turns of the hairspring.  I was able to knock them apart, but if it impacts timing, I may have to immerse the spring in alcohol.  I'm loathe to do that because the spring has a nice overcoil and is very, very delicate!

Here is the balance reassembled with the new impulse pin installed in the roller table.


And a zoom-in:

 
But the balance reassembly did not entirely go well the last time...  I bumped the attachment point with the tweezers, and snapped the spring at the balance attachment point.  Previously, I had thought it nice that there was a removable clamp that made removing the balance easy.  However, that clamp was installed very permanently onto the hairspring.  It took a good two hours to remove the old pin (brass, extremely tightly fit; I think it was staked in place at the factory!), fashion a new pin (I used soft copper, and much longer, since I wanted be able to get it out in the future if needed), and get everything back to working order.  As wooden clockmaker Clayton Boyer says, "Mistakes take a lot of time. I spend some of my best woodworking time making them."  Yeah, I agree.

Still, after all that, the watch still would not run.  What!?!  No visible trouble... actually, not.  I had never worked with a watch with an overcoiled hairspring.  It can happen that the overcoil turn can foul on both the balance cock and the main turns of the spring.  That was the problem.  A very slight touch on the spring attachment point fixed the overcoil's path, and the watch sprung to life!

The movement is now running, which is a relief!  It sounds different from the other movements I've repaired, because it's quite a bit lower frequency (around 2 Hz) than other movements of the same size (typically 4-6 Hz).  Assuming it all goes back together, I wonder if it will keep reasonable time?

One final thing, though.  The winding works for this watch is not the usual Swiss mechanism.  It's a bit simplified, which seems elegant at first.  Here it is when correctly assembled.



However, should the stem get loose and you simply try to reinsert it, you will likely knock the cylinder gear assembly off its retaining spring.  This is rather subtle.  In the picture below, the lower retaining spring is supposed to be running in the cylindrical groove right below it.  All you need to do to repair it is slip the stem back in, and push the spring down gently.  It reseats easily, and then you can carefully withdraw the stem, leaving everything in place.


This process is extremely annoying, because although fixing it takes mere seconds, to access this mechanism you have to uncase the movement, dismantle the hands, and dismantle the dial.  Reassembling the movement into the case involves reinserting the stem, which has a tendency of knocking the winding mechanism out of order... so you need to back up, disassemble everything and try again...

Sunday, April 12, 2020

Astrolabe cases

Two sets of friends are getting married, and as both couples are intellectually curious, I thought an astrolabe would be a nice gift.  But astrolabes alone require some kind of protection... so I decided to make cases for them.

I started from a block of black walnut cut from a tree we had taken down earlier this year.  Since I had previously split it, the wood had been drying all summer in the back yard.

Mostly, the woodworking needed for the boxes was nothing particularly special.  The steps I did were:
  1. Rough cut the block of wood into blocks, each about 2 inches larger than my intended final size.  I used a chainsaw for this, and did the work outside.
  2. Power planed the blocks so that the edges were square and partially smooth.  Since my power planer makes an enormous mess, I also did this outside.  (The chips from the chainsaw and power planer go in my compost...)
  3. Using a large hand crosscut saw, I sliced off the lids of the boxes.  This is a somewhat delicate operation -- even though it requires lots of force -- as you must ensure that the cut is perfectly planar and parallel to (at least one of) the faces of the block.  I don't have a large enough power saw blade, so this is also a manual step!  In all honesty, this is a ripping operation, so I should have used a rip saw... but I don't have one.  My crosscut saw works well enough.
  4. I did an initial sanding of the cut surfaces and did a little bit of squaring up of the other faces.
  5. I recessed the parts of the box that receive the astrolabe.  This involved tracing the outline of a (disassembled) astrolabe to where the recess needed to go on both the base and the lid of the box.  I then used a router in 1/16" depth increments to cut the recess.  For the base, the recess is stepped since the thumb ring is supported in a more shallow recess than the rest of the astrolabe.  This also gives room for the pointers.  I also recessed the lid.
  6. Power belt sanding.  Lots of it!  Starting with 60 grit, I got all faces parallel and square and cleaned off all the cut marks from the saws and planes.  I also rounded the edges where I wanted them round.  Then I repeated the whole process  with 80, 100, 150, and 180 grit.
  7. Since I wanted a very fine finish, I then hand sanded the entire box with 220, 320, and 400 grit sandpaper.  Walnut will polish nicely with finer sandpaper if you're planning for an oil finish, but that wasn't necessary for this project.
  8. Five coats of polyurethane with plenty of time for drying, and 400 grit hand sanding between each coat.  I made sure that the recesses were left unfinished, since I wanted to adhere a velvet lining.
I wanted to line the inside of the boxes with velvet to protect the astrolabe.  Since the cast acrylic I have been using recently for astrolabes is actually fairly sturdy, a velvet-lined box is surely overkill.  (I did accidentally drop my larger astrolabe, and that shattered the thumb ring.  Since super glue is actually an acrylic, it was a simple matter to fix the crack.  Super glue leaves a mostly invisible joint on acrylic and bonds almost instantly.)

Velvet is a fairly troublesome material for lining.  To make it adhere to a flat surface inside the box, you must support it.  The usual way this is done is to glue the velvet to a sheet of cardboard first, and then glue the cardboard to the box.  Since velvet frays badly, you need to roll the velvet around the back of the cardboard (a second gluing) so that no cut edges show.  Finally, since the boxes have a circular cutout to fit the astrolabe, I had to figure out how to manage that joint.

In the end, I glued the cardboard to the velvet, rolled and glued the edges, but left the circular bottom edge alone.  After the glue dried, I hand stitched the circular bottom edges together.  The result was a stiff velvet "cup" that fits tightly inside the box.


Once the velvet was glued in place, I added hinges and a front clasp.  While hinges and clasps aren't difficult to install, they require precision.  You must be especially careful since you don't want to harm the finish.  I held the box in the vice, but lined it with soft paper towel so that the finish wasn't marred by the vice.  I sharpened (under a microscope) my 1/16" drill bit before starting.  To install the tacks for the clasp, I didn't strike the tacks with the hammer directly, but rather used a recessed punch to ensure that I didn't slip and damage the finish.  When setting the tacks, I also held them in brass tweezers.